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Weathering and Erosion

Weathering and Erosion. Weathering. The breakdown do the materials of Earth’s crust into smaller pieces.... (SLOWLY!!!) . Arches National Park, Utah. Physical Weathering. Process by which rocks are broken down into smaller pieces by external conditions. Types of Physical weathering

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Weathering and Erosion

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  1. Weathering and Erosion

  2. Weathering • The breakdown do the materials of Earth’s crust into smaller pieces.... (SLOWLY!!!) Arches National Park, Utah

  3. Physical Weathering • Process by which rocks are broken down into smaller pieces by external conditions. • Types of Physical weathering • Frost heaving and Frost wedging • Plant roots • Friction and impact • Burrowing of animals

  4. Frost Wedging

  5. Plant Roots

  6. Burrowing of Animals

  7. Chemical Weathering • The process that breaks down rock through chemical changes. • The agents of chemical weathering • Water • Oxygen • Carbon dioxide • Living organisms • Acid rain

  8. Living Organisms • Lichens that grow on rocks produce weak acids that chemically weather rock (SLOWLY!!)

  9. Acids created by the roots of plants can dissolve rock!!

  10. Water slowly dissolves rock... • Limestone is the easiest to dissolve.... • Creates “karst” features

  11. Features of Karst: Caves

  12. Features of Karst: Sinkholes

  13. Erosion • The breakdown of the materials of Earth’s crust into smaller pieces.... (FAST!!!) Kali Gandaki River, Nepal

  14. Rivers erode by rolling boulders across hard bedrock • As smaller pieces are created, they are transported downstream Switzer Falls, Pasadena, CA Taroko Gorge, Taiwan

  15. Sometimes rivers don’t have enough energy to move all the rock • Rock can be temporarily deposited in gravel-bars until large spring floods roll • them further along Jasper National Park, Canada South Island, New Zealand

  16. Rivers usually cut “v-shaped” valleys that can be very narrow • Steep canyon walls can collapse by landslides Arun River, Nepal

  17. Glacial Erosion • Snow falls in the high mountains and turns to ice • Ice flows downhill (due to gravity) • Ice erodes rock at base and sides of glacier

  18. Glaciers are a FAST process. • Glacial ice flows like a river, reaching maximum speeds of 20-30 meters/day!!! • Glaciers can remove up to a few mm per year of bedrock Patagonia Ice Cap, Chile

  19. Glaciers erode by grinding rocks against each other, often leaving scrape marks • Glaciers also erode by “plucking” boulders from cliff faces Beartooth Mountains, Montana Sierra Nevada, California

  20. U-shaped valleys • Because glaciers are wide they often erode flat-bottomed “u-shaped” valleys • Thick ice can support very steep-walled valleys that collapse when ice melts Kings Canyon, California Sierra Nevada, California

  21. Glacial Moraines • Glaciers erode rock from cliffs and push it into big piles called moraines • Moraines are self-supporting (not attached to hillside or mountain) • Often shaped like a snake, with lots of curves. Steep sides. Chugach Range, Alaska Durango, Colorado

  22. Wind Erosion • In dry areas, sandstorms can blow sand at up to 70 miles per hour!! • Blowing sand grains act as sandpaper to erode rock surfaces (and more!) Soldier in Iraq US military base, Iraq

  23. Wind erosion can create distinctive patterns of interconnected holes the planet Mars Seminole Canyon State Park, texas

  24. “Hoodoos” are created by wind erosion • Soft layers of rock erode more easily than hard layers of rock • Eroded columns of rock are often attached at the base

  25. Bryce Canyon National Park, Utah

  26. Big sand storms can be viewed from space!! West Africa Persian Gulf

  27. Landslides and Rockfalls • Landslides often produce scoop-shaped “scarps” at the top • Angle gets shallower at deeper depths • Debris in runout area

  28. What causes landslides? • Oversteepened slopes • Landslides often occur in soft rock or thick soils • Landslides can be triggered by heavy rain • or earthquakes La Conchita, California (highway 1 0 1 between Santa Barbara and Ventura )

  29. Rockfalls occur when very hard bedrock has been oversteepened by • rivers or glaciers • Rock breaks off in slabs, rather than the scoops typical for landslides Y osemite National Park, California

  30. Coastal Erosion Ireland Pacifica, California

  31. Pressure from waves and rocks • creates cracks in rock • Overhanging cliffs collapse • Rolling rocks create flat • “wave-cut terraces”

  32. Wave cut terraces can be tectonically uplifted and preserved • New ones are being formed at the base of the old ones!! • Look for these all over southern California!! Montagne de Oro, California Santa Barbara, California

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